Hands-free audio systems in automobiles can be used without the use of hands (for example via voice commands) or, in a wider sense, with relatively limited use of hands such that a telephone handset does not need to be held in the driver's hand while the driver is driving an automobile.
Automotive hands-free audio systems commonly use one or more of the vehicle's speakers to transmit the voice of the person on the other end of the telephone call, and one or more microphones in the vehicle to capture the driver's and/or passengers' voices during telephone calls.
A mobile phone is commonly connected to an automotive audio system head unit or a telematics unit in the vehicle via Bluetooth. Or the head unit or telematics unit could have its own network access device (NAD). In such a system, as the microphone signal goes through the system, the signal is processed and sent to the person on the other end through the mobile phone or NAD. The speech from the far end is coming through the phone (through the Bluetooth) or NAD, being processed, and then comes out of the speakers.
At the microphone in the vehicle, there could be near end speech, background noise, wind noise, and echo, which is the audio coming from the audio-system speakers and which is also being picked up by the microphone. When the person on the far end is speaking, that person doesn't want to hear their echo, the road noise, or the wind noise. So, the echo is typically cancelled, the road noise is typically suppressed, which are common features, but noise-suppression techniques that dynamically increase noise suppression based on input noise characteristics would improve the performance of a hands-free audio system, for example, by improving the sound quality at the far end of telephone conversations in which an automotive hands free audio system is being used and/or by improving speech-recognition performance of a voice-controlled application.